cv2 画多边形不填充_OpenCV python: 任意多边形填充和凸多边形填充（fillPoly和fillConvexPoly的区别，有图有真相！）...

我们经常会使用contour或者自己圈出来的区域填上对应的值或者，所以经常会使用这样两个函数：fillPoly和fillConvexPoly，至于这两个函数有什么区别呢？小伙伴从题目中就可以看出来了，一个是任意多边形进行填充(有可能是非凸的)，一个是对凸多边形进行填充。

两个函数的使用方法和说明：

官方文档：函数fillConvexPoly绘制一个填充的凸多边形。 该函数比函数fillPoly快得多。 它不仅可以填充凸多边形，而且可以填充任何不具有自相交的单调多边形，即，其轮廓与每个水平线(扫描线)相交的多边形最多两次(尽管其最顶部和/或底部边缘可能是 水平)。

def fillConvexPoly(img, points, color, lineType=None, shift=None): # real signature unknown; restored from __doc__

"""

fillConvexPoly(img, points, color[, lineType[, shift]]) -> img

. @brief Fills a convex polygon.

.

. The function cv::fillConvexPoly draws a filled convex polygon. This function is much faster than the

. function #fillPoly . It can fill not only convex polygons but any monotonic polygon without

. self-intersections, that is, a polygon whose contour intersects every horizontal line (scan line)

. twice at the most (though, its top-most and/or the bottom edge could be horizontal).

.

. @param img Image.

. @param points Polygon vertices.

. @param color Polygon color.

. @param lineType Type of the polygon boundaries. See #LineTypes

. @param shift Number of fractional bits in the vertex coordinates.

"""

pass

官方文档：函数fillPoly填充由多个多边形轮廓所界定的区域。 该功能可以填充复杂的区域，例如，带有孔的区域，具有自相交的轮廓(部分轮廓)等等。

def fillPoly(img, pts, color, lineType=None, shift=None, offset=None): # real signature unknown; restored from __doc__

"""

fillPoly(img, pts, color[, lineType[, shift[, offset]]]) -> img

. @brief Fills the area bounded by one or more polygons.

.

. The function cv::fillPoly fills an area bounded by several polygonal contours. The function can fill

. complex areas, for example, areas with holes, contours with self-intersections (some of their

. parts), and so forth.

.

. @param img Image.

. @param pts Array of polygons where each polygon is represented as an array of points.

. @param color Polygon color.

. @param lineType Type of the polygon boundaries. See #LineTypes

. @param shift Number of fractional bits in the vertex coordinates.

. @param offset Optional offset of all points of the contours.

"""

pass

用起来也相当方便了，写了个小例子

import cv2

img_star = cv2.imread("../test_imgs/star.jpeg")

img_star_gray = cv2.cvtColor(img_star, cv2.COLOR_BGR2GRAY)

kernel =cv2.getStructuringElement(cv2.MORPH_RECT,(5,5))

retval, dst = cv2.threshold(img_star_gray, 0, 255, cv2.THRESH_OTSU)

cv2.imshow("bin: ", dst)

cv2.waitKey(0)

contours, _ = cv2.findContours(dst, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)

cv2.fillPoly(img_star, [contours[0]], (0,255,255))

#cv2.fillConvexPoly(img_star, contours[0], (0,255,255))

cv2.imshow("dst: ", img_star)

cv2.waitKey(0)

cv2.destroyAllWindows()

下载了一颗五角星，这个效果会比较明显：

我们先进行二值化：

使用cv2.fillPoly进行填充：

使用cv2.fillConvexPoly进行填充：

这个例子应该相当明显了(≧▽≦)/啦啦啦！

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